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11 Emissions Sampling of Combustion Effluents from a Stationary Diesel Engine That Burns a Coal-Derived Liquid Fuel

Downloaded by UNIV LAVAL on July 12, 2016 | http://pubs.acs.org Publication Date: September 18, 1986 | doi: 10.1021/bk-1986-0319.ch011

W. Püspanen, P. Webb, and D. Trayser Battelle Memorial Institute, Columbus Laboratories, Columbus, OH 43201

The emissions from a utility diesel engine burning a middle distillate Exxon Donor Solvent (EDS) coal l i q u i d and diesel fuel (DF-2) were measured as part of a program designed to evaluate the feasibility of the use of coal derived fuels in utility d i e s e l s . The t e s t program included various engine loads and EDS/DF-2 blend ratios. Also, higher and lowerairmanifold temperatures (AMT) were evaluated. The r e s u l t s indicated that an EDS/DF-2 blend of up to 66.7 percent EDS was usable in the engine. Full engine t e s t s showed that the p a r t i c u l a t e emissions were increased with increasing amounts of the EDS f u e l . The e f f e c t of EDS fuel on NO emissions was less clear. TheSO emissions were low and were unchanged by EDS/DF-2 blend ratios. X

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The purpose of t h i s program was to define f o r utility diesel systems what engine and operating condition modifications might be necessary to accommodate the use of coal l i q u i d f u e l s . Coal l i q u i d s ( i . e . , SRC I I , EDS, etc.) have been shown to burn quite r e a d i l y U>2); however, certain of t h e i r known physical and chemical c h a r a c t e r i s t i c s are l i k e l y to influence t h e i r s u i t a b i l i t y f o r engine use. Among these are: 0 0 0 0 0

Low cetane number High f l a s h and d i s t i l l a t i o n points High aromatic content High nitrogen content High s u l f u r content.

The low cetane number of coal l i q u i d fuels could lead to poor s t a r t i n g and warm-up c h a r a c t e r i s t i c s at low ambient temperatures and to engine roughness at part load operation. 0097-6156/86/0319-0124506.00/0 © 1986 American Chemical Society

Markuszewski and Blaustein; Fossil Fuels Utilization ACS Symposium Series; American Chemical Society: Washington, DC, 1986.


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In a d d i t i o n , low cetane fuels have been shown to r e s u l t in increased combustion chamber deposits and higher smoke or p a r t i c ulate emissions. A higher f l a s h point might a f f e c t the safety of the fuel in storage but is not l i k e l y to influence engine operations. A higher d i s t i l l a t i o n point, on the other hand, may lead to longer i g n i t i o n delay, n e c e s s i t a t i n g a change in i n j e c t i o n timing, and poorer fuel vaporization and mixing of the i n j e c t e d fuel with the a i r charge in the combustion chamber. The hydrogen content of coal is about 5 percent. In the conversion process (to l i q u i d f u e l ) the p a r t i a l hydrogénation increases the hydrogen content to about 10.6 percent f o r the EDS f u e l . Petroleum-based d i s t i l l a t e f u e l s have a hydrogen content in the range of 12 percent; however, the higher aromatic content in the raw coal generally r e s u l t s in an aromatic content in the coal l i q u i d f u e l , a f t e r hydrogénation, considerably higher than the petroleum f u e l . This higher aromatic content could cause higher hydrocarbon and/or p o l y c y c l i c aromatic (POM) emissions. The emissions of N0 from d i s t i l l a t e o i l fueled diesel generators represent a major a i r emission source. The use of synfuels presents an additional N0 problem f o r diesel generators in that raw (unhydrotreated) l i q u i d s often contain s i g n i f i c a n t l e v e l s of both s u l f u r and nitrogen with the heteroatom concentration increasing with b o i l i n g range. The f a c t that the EDS fuel has a low fuel nitrogen content (0.1 percent) could prove valuable in its use as a diesel f u e l . Manufacturers of diesel engines generally recommend that fuels which contain less than 0.5 percent s u l f u r be used in order to minimize corrosion problems. A typical diesel fuel has approximately 0.15 percent s u l f u r though there is a wide variation in d i f f e r e n t f u e l s . The use of EDS fuel with a s u l f u r content of 0.4 percent could present a possible problem with regard to both SO2 and SO3 emissions. X

X

Technical Approach For t h i s program a Cooper LSV-16-GDT 16-cylinder, 4-stroke, turbocharged engine was used to evaluate various blends of EDS and a standard DF-2 f u e l . The engine was owned and operated by a public utility company. Cooper Energy Services designed a test matrix f o r the evaluation of fuel blends at d i f f e r e n t engine operating conditions and supervised the actual engine t e s t operations. B a s i c a l l y , three operating parameters were varied: the fuel blend r a t i o as EDS/DF-2, the a i r manifold temperature (AMT) and the engine/speed load conditions as kilowatts (kw) of e l e c t r i c a l power at rated speed. In addition a s p e c i a l l y designed sampling system was used to evaluate extreme blend r a t i o s and test engine modifications applied to only one of the 16 cylinders. Baseline t e s t s on the DF-2 fuel were made at the various t e s t conditions f o r comparative purposes.



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FOSSIL FUELS UTILIZATION: ENVIRONMENTAL CONCERNS

Sampling f o r gaseous emissions was conducted at two locations of the engine exhaust. In one location a rake-type probe with a heated sampling l i n e was used to continuously withdraw samples of the exhaust gas before it entered the s i l e n c e r . A special check-valve sampling probe was i n s t a l l e d f o r a l t e r n a t i v e single cylinder exhaust gas monitoring. Provision f o r SO2/SO3 sampling was included in both sample l i n e s . The sampling f o r SO2/SO3 was by a c o n t r o l l e d condensation system based on an o r i g i n a l design by Goksoyr and Ross (3), followed by a hydrogen peroxide impinger t r a i n . This system is now referred to as the Goksoyr-Ross t r a i n and methods f o r operation are documented by both the U.S. EPA and the APHA. Sampling f o r p a r t i c u l a t e s was by a standard EPA Method 5 probe and impinger t r a i n . The method was modified by adding NaOH to the second impinger to allow determination of c h l o r i d e emissions. The Method 5 sampling was conducted at the outlet of the s i l e n c e r using two perpendicular sampling ports and multiple point traverses. For the program, r e p l i c a t e tests were conducted when f e a s i b l e . Duplicate measurements were made of SO2 (EPA Method 6 and an NDIR instrument) and of N0 (EPA Method 7 and chemiluminescence instrument). Analyses of p a r t i c u l a t e , SO2/SO3 and CI were made o n s i t e . A l l gas moni t o r i n g instruments were zeroed and spanned d a i l y using c e r t i f i e d span gases. X

Test Results Fuel Analyses. P r i o r to actual sampling the fuel blends were analyzed by Southwest Research Institute (SWRI) and reported in t h e i r report to EPRI on t h i s project (4). The cetane number of the fuel blends ranged from 49.6 f o r 100% DF-2 to 21.0 f o r 100% EDS. The higher heating value (HHV) ranged from 19,500 Btu/lb ( f o r 100% DF-2) to 18,569 Btu/lb ( f o r 100% EDS). The nitrogen and s u l f u r content were v a r i a b l e but reported by SWRI as 0.09 percent s u l f u r and 0.12 percent nitrogen. This s u l f u r content is lower and the nitrogen is higher than most conventional diesel f u e l s . The DF-2 s u l f u r content was also low at 0.15 percent. The H/C r a t i o of the EDS was somewhat lower than the DF-2 (approximately 0.11 compared to 0.16), i n d i c a t i n g a higher degree of aromatic constituents. Baseline Tests. Baseline diesel tests were conducted at constant speed (360 rpm) and four generating loads, No Load, 1800 kW, 2600 kW, and 3600 kW. A l l tests were conducted at 110° F AMT except f o r the 3600 kW condition which a l s o included 150° F AMT and 95° F AMT t e s t s . The r e s u l t s of p a r t i c u l a t e emissions t e s t i n g at four conditions of 0 Blend are l i s t e d in Table I. The r e s u l t s include both the 95° F AMT and the 150° F AMT tests which indicate the observed reduction in p a r t i c u l a t e emissions with increased AMT.


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Table I. Baseline Test P a r t i c u l a t e Emissions Load

(kW)

AMT


2,650 3,570 3,590 3,590

110 110 149 95

(°F)

Fuel Rate (Btu/kWhr)

(lb/ΜΜ Btu)

(ng/J)

9,950 9,910 10,010 9,900

.018 .028 .016 .028

7.7 12.0 6.9 12.0

The gaseous emissions were comparable to those reported in other tests of d i e s e l generators burning No. 2 d i e s e l fuel (5). The O2 ranged from 10.8 percent at 3600 kW to 18.2 percent at FSNL (Full Speed No Load). As expected, the CO2 increased with load. The CO was s l i g h t l y higher than expected, up to 195 ppm at 3600 kW, i n d i c a t i n g less than optimum performance. The SO2 concentrations were low, r e f l e c t i n g the low s u l f u r content of the f u e l . Gaseous Emissions from Blend Test. Tests were conducted f o r the various blend r a t i o s and load conditions. The r e s u l t s from the stack emissions measurements f o r the f u l l engine t e s t s are summarized in Table I I . This table provides averages f o r each engine load condition as measured at the baseline fuel condition and f o r the three blend r a t i o s . As was observed in the baseline t e s t s , the CO2 increased with engine load while O2 decreased. There was no observed e f f e c t of blend r a t i o on SO2 emissions, although SO2 did increase s l i g h t l y with increas ing load as would be expected. The N0 , when corrected to 15 percent O2 (dry), showed a s i g n i f i c a n t increase as load was increased to 1800 kW and then a more gradual increase up to the maximum load of 3600 kW. The r e s u l t s of gaseous monitor ing f o r the baseline and maximum blend t e s t s at AMT of 95°F and 150°F are included in Tables III and IV. The 3600 kW baseline emission t e s t s f o r 95° F and 150° F AMT were comparable to the 110° F AMT t e s t s . The gaseous emissions showed no s i g n i f icant changes between operating temperatures except that the corrected N0 appeared to increase s l i g h t l y at 110°F AMT compared to 95°F. The maximum blend t e s t s were both s l i g h t l y higher than the 110° F AMT 0 blend but an additional test at 2600 kW and 150° F AMT showed a corrected N0 value of 946 ppm which was below the 110° F AMT value. X

X

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P a r t i c u l a t e Emissions from Blend Tests. The stack p a r t i c u l a t e emissions f o r the baseline and three blend r a t i o s were measured. The e f f e c t of blend r a t i o s on the p a r t i c u l a t e emission rate is shown g r a p h i c a l l y in Figure 1. In t h i s representation the percent increase of the p a r t i c u l a t e emission rate over the baseline value f o r the various blend r a t i o s is plotted f o r the two higher engine loads at 110° F AMT. The e f f e c t of blend r a t i o on the p a r t i c u l a t e emissions is s i g n i f i c a n t . The increase in the rate over baseline is


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Table II. Average Stack Gaseous Emissions Data Summary For Full Engine Tests (From Reference 6) THC N0 CO O2 SO2 NO (ppm) (ppm) (ppm) (percent) (ppm) (ppm) 0 Percent Blend, AMT = 110°F 453 206 178 18.2 67 —* 1.8 FSNL 1800 5.6 87 13.2 73 803 816 142 2600 6.2 93 12.0 72 833 983 153 7.2 161 10.8 80 962 997 166 3600 25 Percent Blend, AMT = 110°F 516 273 345 18.5 54 349 1.8 FSNL 1800 7.8 105 13.3 60 766 835 155 2600 6.6 105 12.0 58 895 160 3600 7.2 175 11.1 55 1089 205 50 Percent Blend, AMT = 110°F 601 390 725 18.3 56 458 1.9 FSNL 1800 6.0 110 13.0 56 907 117 2600 6.7 124 12.0 64 862 120 3600 7.4 162 11.0 62 1158 128 667 Percent Blend, AMT = 110°F 540 750 1200 18.5 50 388 1.8 FSNL 1800 6.1 110 12.9 59 974 1007 108 2600 6.9 116 11.8 61 998 105 3600 7.3 170 11.2 62 1138 122 •Indicates data deleted due to malfunction o f instrument. Note: NO and N0 data are corrected to 15 percent O2. Source: Reproduced with permission from Ref. 6. Copyright 1983 E l e c t r i c Power Research I n s t i t u t e .


Load (kW)

C0 (percent)

X

2

X

Table I I I . Stack Emissions Data Summary For 3600 kW at 95° F AMT THC CO O2 SO2 N0 Blend C0 (ppm) (percent) (ppm) (ppm)(ppm) (percent) (percent) 140 145 11.0 82 894 7.0 0 135 115 11.5 70 1006 7.0 67 2

X

Table IV. Blend (percent 0 75

Stack Emissions Data Summary For 3600 kW At 150° F AMT THC CO O2 SO2 N0 C0 (ppm) (percent) (ppm) (ppm)(ppm) (percent 185 170 10.5 71 858 7.4 168 130 11.3 67 1046 7.2 2

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PIISPANEN E T A L .

Figure 1. Particulate mass rate increase as affected by blend r a t i o , engine load, and AMT.



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approximately the same f o r the two conditions load at 110° F AMT. In terms of actual emissions rate based on mass of p a r t i c u l a t e per heat input, the 50 percent blend at 2600 kW and 110° F AMT was lowest (10.2 ng/J) while the 66.7 percent at 3600 kW and 110° F AMT was the highest (20.9 ng/J). A test of 75 percent blend at 3600 kW and 150° F AMT was observed to have a lower p a r t i c u l a t e emission rate (16.1 ng/J) than the reported highest value, and s i m i l a r l y a baseline t e s t of 3600 kW and 150° F AMT showed a 42 percent lower p a r t i c u l a t e emission rate than e i t h e r the 95° F AMT or the 110° F AMT baseline as shown in Table I . This suggests that increasing the AMT may reduce the p a r t i c u l a t e emission rate. Other Gaseous Emissions. Emissions samples f o r SO3 and c h l o r i d e s measurements were a l s o included in t h i s program. In t o t a l , 12 samples f o r SO2/SO3 measurement were obtained; 6 were in the stack location and 6 were in the single c y l i n d e r configura t i o n . No SO3 was detected in any of the samples by the standard t i t r a t i o n with 0.02 Ν NaOH. In each of the tests f o r p a r t i c u l a t e emissions conducted in t h i s program, an impinger sample was c o l l e c t e d f o r CI determination by AgCl gravimetric method. In a l l cases there was no p r e c i p i t a t e formation i n d i c a t i n g chlorides were less than the detectable l i m i t . Conclusions The use of EDS/DF-2 fuel blends in utility d i e s e l s provides an acceptable a l t e r n a t i v e of conventional petroleum-based fuel operation. A blend r a t i o of approximately 66.7 percent EDS and 33.3 percent DF-2 can be used without engine knocking at an AMT of 110° F. At an AMT of 150° F t h i s r a t i o can be extended to 75 percent EDS. The major impact of the use of EDS blends appears to be an increase in the p a r t i c u l a t e emissions rate. The e f f e c t of EDS/DF-2 blends on p a r t i c u l a t e emissions was s i g n i f i c a n t l y influenced by both blend r a t i o and engine load. Increasing one or the other or both r e s u l t e d in an increase in the p a r t i c u l a t e emissions, though an increase in AMT may reduce the p a r t i c u l a t e emission rates. No information on p a r t i c l e s i z e or morphology was obtained in t h i s program. The results of the exhaust stack measurements of gaseous emissions indicate that the use of EDS/DF-2 fuel blends under engine load conditions resulted in a moderate increaseinCO emissions (25%) and a moderate decrease in THC emissions (26-31%) when compared to baseline (0%) t e s t s . The EDS/DF-2 fuel blends a l l showed substantial increases in both CO and THC emissions at the no-load c o n d i t i o n . The emissions o f N0 from EDS blends are less than or equal to the baseline over a l l engine loads except f o r the maximum EDS/DF-2 blend where N0 l e v e l s were s l i g h t l y higher at lower loads. A 150° F AMT s l i g h t l y increased the N0 f o r baseline and the 66.7 percent blend at 3600 kW but lowered X

X

X


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the 2600 kW concentration. The overall average percent o f NO2 in the N0 a t baseline conditions was approximately 9 percent. Due to problems with the NO analyzer, the e f f e c t o f AMT and blend r a t i o on N0 could not be determined. There was l i t t l e c o r r e l a t i o n between blend r a t i o s and SO2 emissions, a l l o f which were r e l a t i v e l y low. Measurements of SO3 and CI were below the expected lower l i m i t s and thus the potential f o r corrosion should be minimal in the use o f EDS/DF-2 blends. X

2


Acknowledgments This work was supported by EPRI through the Advanced Power Systems D i v i s i o n . Mr. Henry Schreiber was the Project Manager. F i e l d sampling was conducted by B a t t e l l e Columbus personnel Paul Webb, Harry Leonard and William Baytos. Cooper Energy Services and Easton U t i l i t i e s provided technical assistance and operated the fuel handling and engine systems during the tests. Literature Cited 1.

2.

3. 4.

5.

6.

Piper, B. F.; Hersch, S.; Nazimowitz, W. "Combustion Demonstration of SRC II Fuel Oil in a Tangentially Fired Boiler"; Report No. EPRI FP-1029, Electric Power Research Institute; Palo Alto, CA, 1979. Downs, W.; Kubasco, A. J. "Characterization and Combustion of SRC II Fuel Oil", Report No. EPRI FP-1028, Electric Power Research Institute; Palo Alto, CA, 1979. Goksoyr, H.; Ross, K. J. Inst. Fuel, 1962, 35, 177. Ariga, S; Baker, Q. A. "Evaluation of Exxon Donor Solvent (EDS) Coal Liquid as a Utility Diesel Fuel"; Report AP-3224, Electric Power Research Institute: Palo Alto, CA, 1983 Shih, C. C.; Hammersma, J. W.; Ackerman, D. G.; Beimer, R. G.; Kraft, M. L . ; Yamada, M. M. "Emission Assessment of Conventional Stationary Combustion Systems: Volume II, Internal Combustion Sources," U.S. EPA Report No. EPA-600/7-79-029C, 1979. Piispanen, W.; Webb, P.; Trayser, D. "Emissions Sampling for Utility Diesel Synfuel Tests"; Appendix Β in Report AP-3224, Electric Power Research Institute: Palo Alto, CA, 1983.

RECEIVED March 31, 1986


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